Agricultural machinery such as (but not limited to) harvesters, tractors, mowers, shakers, balers, threshers, and mulchers typically operate in environments where they are exposed to combustible vegetation material. The combustible vegetation material, such as dry grass, hay and wheat stems, can smoulder and eventually ignite if it comes into contact with various external portions of an internal combustion engine. This is a result of the high internal operating temperatures present within the engine, and the presence of heated exhaust gasses.
Silencers or mufflers are connected to the exhaust system of most internal combustion engines. A muffler is intended to reduce the sound pressure of the exhaust gasses, and hence reduce the noise output by the engine. There are numerous types of mufflers which are commercially used. However, one factor common to all mufflers is the generation of a significant amount of heat.
It is known for combustible vegetation material to foul or build up on those parts of an internal combustion engine which become heated, such as the muffler. In particular, combustible material is known to accumulate on or around the silencer or muffler of internal combustion engines used to power agricultural equipment.
Agricultural equipment, such as harvesters and the like, have sometimes been destroyed by fire caused by a build-up of debris on or close to hot engine components of internal combustion engines used to power such equipment. As a result, not only is there a risk of the agricultural equipment being destroyed or badly damaged, but such fires can conflagrate to larger fires, which can destroy large areas of bush and/or crops, building assets, and other equipment.
It is sometimes necessary for a user to access the engine compartment of agricultural equipment, for maintenance, repair and operational purposes, and accidental contact with hot parts of the engine has been known to cause serious personal injury. In a typical arrangement, an item of agricultural equipment has an internal combustion engine fitted with a cooling fan arranged to direct air past the engine and having an exhaust with a silencer mounted substantially parallel to a hood or bonnet and transverse to the flow of air directed by the cooling fan. Hereinafter, this arrangement will be referred to as an internal combustion engine of the type described, unless the context indicates otherwise.
Agricultural machinery such as harvesters pose a significant risk of burn injuries in respect of the muffler, as the engine is typically compact, and hence the muffler is located relatively close to the engine. The reduced exhaust manifold distance between the engine and the muffler results in high temperatures occurring on the surface of the muffler, which after prolonged periods of engine use may result in very high muffler temperatures.
Another known problem with some agricultural machinery is the issue of engine noise. The high levels of power required for some agricultural products, and the proximity of the driver/operator to the engine, dictate that noise levels are often significantly greater than would be acceptable in the design of comparable consumer use vehicles.